Centuries of intense surface melt on Larsen C Ice Shelf

• Main Authors: Bevan, Suzanne, Luckman, Adrian, Hubbard, Bryn, Kulessa, Bernd, Ashmore, David, Kuipers Munneke, Peter, O'Leary, Martin, Booth, Adam, Sevestre, Heidi, McGrath, Daniel
• Format: Article in Journal/Newspaper
• Language: unknown
• Published: 2017
• Subjects: Antarctic; Antarctic Peninsula; Cabinet Inlet; The Antarctic; Antarc*; Ice Shelf
• Online Access: http://livrepository.liverpool.ac.uk/3033960/; https://doi.org/10.5194/tc-2017-81

<jats:p>Abstract. Following a southward progression of ice-shelf disintegration along the Antarctic Peninsula, Larsen C Ice Shelf is the focus of ongoing investigation regarding its future stability. The ice shelf is known to be experience surface melt, and commonly features surface meltwater ponds. Here, we use a flowline model and a firn density model to date and interpret observations of melt-affected ice layers found within five 90 m boreholes distributed across the ice shelf. We find that units of ice within the boreholes, which have densities exceeding those expected under normal compaction metamorphism, correspond to two climatic warm periods within the last 300 years on the Antarctic Peninsula. The more recent warm period, from the 1960s onwards, has generated distinct sections of dense ice in two boreholes in Cabinet Inlet, close to the Antarctic Peninsula mountains – a region currently affected by föhn winds. Previous work has classified these layers as refrozen pond ice, requiring large quantities of mobile liquid water to form. Our flowline model shows that, whilst preconditioning of the ice began in the late 1960s, it was probably not until the early 1990s that twentieth-century ponding began. The earlier warm period occurred during the 18th century and resulted in two additional sections of anomalously dense ice deep within the boreholes. The first, in one of the Cabinet Inlet boreholes, consists of ice characteristic of refrozen ponds and must have formed in an area currently featuring ponding. The second, in a mid-shelf borehole, formed at the same time in an area which now experiences significant annual melt. Further south on the shelf, the boreholes sample ice that is of an equivalent age but which does not exhibit the same degree of melt influence. This west–east and north–south gradient in past melt distribution resembles current spatial patterns of surface melt intensity. Using flowlines to trace the advection and submergence of continental ice identified in boreholes, we demonstrate ...